The present invention is drawn to a multi-stage compressor and, more particularly, a multi-stage compressor comprising a plurality of series connected compression stages of variable volume wherein the compressor includes a mechanism for automatically lubricating same during the operation thereof. The multi-stage compressor of the present invention may be driven by any suitable drive mechanism such as an internal combustion engine, electric motor or any other device which produces reciprocal movement of a piston rod. The multi-stage compressor of the present invention is particularly useful in compressing fluids, particularly gases, including natural gas, air, nitrogen and the like. The multi-stage compressor of the present invention is particularly useful for compressing gases which are produced at well sites during the production of crude oil from deep wells.